Method of and means for providing cathodic protection of metallic structures



Feb. 17, 1948. MaCTAGGART ETAL 2,435,973

METHOD OF AND MEANS FOR PROVIDING CATHODIC PROTECTION OF METALLIC STRUCTURES Filed Aug. 19, 1941" 4 Sheets-Sheet 1 FIGI.

F G 7 I INVENTOR.

. ARTHUR B. MACTAGGART and GEORGE J. THOMSON 7 Kai ATTORNEYS.

Feb. 17, 1948.

A. B. Ma TAGGART ETAL 2 3 73 METHOD OFAND MEANS FOR PROVIDING CATHODIC PROTECTION OF METALLIC STRUCTURES Filed Aug. 19, 1941 4 Sheets-Sheet 2 INVENTOR. ARTHUR B MACTAGGART an GEORGE J. THOMSON BY 2 Mi ATTORNEYS.

4 Sheets-Sheet x5 I HI H IJI HH HflUUHHH h I l I l l l hfi l Hl l l lldl l l l lJHP l A. B. M TAGGART ET.AL METHOD OF AND MEANS FOR T'ROVIDLNG CATHODIC PROTECTION OF METALLIC STRUCTURES Fi'led Aug 19, 1941 \llllllllllllll llll llrlllll dnfl INVENTOR. ARTHUR B. MACTAGGART 7 BY d GEORGE. J. THOMSON f4 [MK/MM ATTORNEYS Feb. 17, 1948.

1948. A. B. M TAGGART ETAL ,973

METHOD OF AND MEANS FOR PROVIDING YCATHODIO PROTECTION OF METALLIC STRUCTURES Filed Aug. 19, 1941 4 Sheets-Sheet 4 FIG.9.

INVENTOR. ARTHUR B. MAGTAGGART BY and GEORGE J THOMSON ATITORNEYS Patented Feb. 17, 1948 @Mnomc; BROTECTION STRUCBURES "0F manure 1'3. jlige raggart, rdiao, an hearse Tnomsbn, mwmm'u, Ohio; assign'ofs co om V dresser new: Ohio Kpplioation Aug ustTQ, is4 L-fseriail 1%. 461,144

This invention negates, gas "molested, 'tlorheth ads f and means for-pro mu baitliodicpfo tecft nagainst corrosio or metallids'truotuies.

kprfrnary object cifthinvention "is "to "provide a "method of cathodic protection against rusting, itting and orrosmnof-metalne 'dontainers of, "or metallic "struotures "immersed in "aqueous 'e'l'ee trolyte which "method in one for includes the external "application "of resistors of any nature, inoan'deseent or otherwise, either 'by attaching said'resfstorstb su'h metalllc cofitainers'or Structures, or by remote I61 inl usi'on of said resistors in 'acathoaepmtwtion circuit, with jor without the use of anodes for 'ltitrodsjin the cbifitaiheil or surrounding'equeous e'le'jdtro1$ te :A" "further object or the invention is to utilize such surg rim-mars s n'a submerged struotur'es in';a*un1airet1bha1pulsating'eurrefit eir'cuit Whi'eh is obtained "from fctifid AQC, "circuits, in a manner "t t t e said metallic bodies are sumciently"lectronegd' tdtheeontantedbr surrounding electrolyte to oppose the "tendency of such metals to go intosolution. v V

To the accomplishment orjthe' f egblhg" and r'eiatedend'sgs iu invention, then, can sts'forthe means-haematite! fully described an pa ularly minted "out in the laims: the annexed drawings and the following description "setting forth in sewn o'ertain mea s'and one mode or ca ii fi 'ijwfiffi v tiofi, f1 and" mode illustrating, however; r or various ways in which the principle oftli'e ifiiiei-iti'oh rnia'yhe used Fig. 2 is a setional or an ltftifid whibh has been especially dsfg'hed'for use in the circuit ribwn'in-Fi'g; '1; m a

Fig. 3 is a diagrammatic View "of "a 'rno'difled elevation amend elevation vies of the resistanp es used in the circuit ofFlQB": v I Figsg'zga, "and '9 show other modifications of theeathb'di iiriitdtiu ciiii'it. W I

,Referfih'g more 'particularliifto' Fig. of the drawings, A designates a stib 'dovvh transformer ha'iifnfi'iiieahs of olita'imnvaiiable reduced soe ondary voltages from tap switches B.- Linesfrorn the tap swi'tohes re conjugated to the full wave dry plate 'brid'gerotifier 'C; which is shown as embodying "Your min-wave 'reotifiers conne'ted in mo'difiefl'brldgearrangement provid'ing 'tWo'hegthe metallic container G and th e other to a, am

a'djace' t the bottom or the epntamer, fern t;

tween half-wave uni v I I m long as burfehti's upp 1edto' thefrehtlfiei a source of alternating current, thefinietallie c' taiher'is fang remains "the'fneg'a'tive "sme'm a p gating D. '0. urban, Th'ejfhailf- 'e" 'r'ee fie'r units as shown prof/idea ti'o'ri"in'opposite fiiictfons' ro" v H dry time fetifir am the hair-wave 1mm tional pulsations are imposed upon spaced points of t e "xhtall'io cbritainer. h

QIth'iis fieytdfore bee "oii'stofif the O K a rb n f e r materials fli'igheinlallyihao'ife" tore considered as best adapted @fbi'th Turn However,-oxy;genev-p1vine faftlie' I "disintg'ifate'sthe ano e su I that any means or suspendm'e thehnod'e'eveh: tual'lyTallS. i H In order to ovfioifiethis. we havedesigii ea an anode, the constructi on of which ls eiearl? shown in Fig. am the dra ings fair ng to this figure; i t Will-be "see dered carbon'o'r graphite 'l'|, witl 1in' which 15 em: 1

bedded a core 18 of insulated wirewhich "ser'ves the dual function of supporting or sus ending the anode and of conducting current from the line Dto the lower endo-f the electrode Withinthe lower end of the anode 'isa oentrallydisposjed; tube IQ of graphite, within which a -brasshplug 20, is disposei' and sealed inn plabe by meffns of a melting compound 21, the w r rg ae i' tthe upper end f thelata ter; and a iii-aw? of tying the casing IE to the wire l8 above said strain relief. In this manner, a closed tube of glass fabric is provided, containing all of the elements necessary to the anode, as well as a means of suspending the latter. Anyclisintegration that occurs merely eifects a gradual settling of the granules within the glass tube and such granules cannot be emitted from the tubing so as to result in disintegration of the anode. Such an electrode is practically indestructible.

It has been definitely determined that, in order to keep a steel water tank from rusting, it is desirable that a potential be applied from an external source as a negative potential of 2 volts are more at the surface of the tank, and the voltage drop across the water must be estiplied at the source. It has further been found that it is necessary to maintain a current flow Moreover, no type of. submerged anode, re-

gardless of its nature, could possibly be expected to withstand the action of ice formation, and it accordingly becomes expedient to provide some means for obviating such electrodes. And, the container can have a negative potential impressed upon it without necessity of any immersed electrode by making the container a part of the circuit and providing suitable voltage-drop conditions. To that end, we have used a combination of resistors, fixed and variable, externally applied, such combinations becoming the positive side of a unidirectional pulsating current circuit and the metallic container the negative side of such circuit. Several types of such resistors are available and they consist of resistance of any nature, incandescent or otherwise, whereby a properly regulated current flow can be maintained.

We use such combinations of resistors for the purpose of applying a load to complete the circuit and regulate a current flow. These can be placed on a metallic container at any point, orthey may be grounded on connecting water pipesgor directly to aground rod of any nature, whereby the current will ultimately return through the metallic container which is serving as the negative connector between units of the rectifier and the negative side in the unidirectional pulsating circuit. I

A typical form of such a, circuit, embodying a resistance potential-drop which substitutes an anode, is illustrated in Figs, 3, 4, 5 and 6 of the drawings. Referring to these figures, and particularly Fig. 3, it will be seen that the circuit is identical with'th'at shown in Fig. l, but that instead of the anode K, the resistance potentialdrop L is used inthe line D, the line from the end thereof being grounded on the conduit H which leads to the-metallic container G. This has the advantageof eliminating immersed electrodes. Figs. 4, 5 and 6 illustrate one type of potential drop, consisting of a fixed resistance 25 and a variable resistance 26 suitably housed in a protecting casing. It may be expedient, however,

4 to use an illuminated or incandescent resistor in place of that shown.

In that form of the invention shown in Fig. 7, the circuit is identical with that shown in Fig. 3, but the line from L, insteadof being connected to the conduit H, is grounded as at 2 1.

In that form of the invention shown in Fig. 8, the circuit is similar to that of Fig. 1, but the line is connected to an anode 28 which is placed in a chamber M, in any conduit, such as the conduit H, which leads to the metallic container of the electrolyte.

In that form of the invention shown in Fig. 9, the line D is grounded, and such ground shall be to some remote point in electrical conductor contact with the metallic container G. Variable or fixed resistors are provided in the negative lines E and F for adjusting the current flow.

While the method has been described more particularly with reference to the cathodic protection of elevated water tanks, it is to be understood that it may be applied to other structures, such as steel water tanks on the ground and in the ground, to pressure tanks, gas holders, filter beds, boil ers, condensers and any other type of metallic.

equipment containing an electrolyte.

Other modes of applying the principle of our 1. The method of protecting a corrodible metallic structure against deterioration in contact with an aqueous electrolyte, which comprises. connecting such structure at spaced points-with plural negative poles of a source of. direct'electric current alternately supplied in low'frequency to said poles, while maintaining a positive pole of such source in electrical connection with such" structure. I

2. The method of protecting, a corrodible metallic structure against deterioration in contact. with an aqueous electrolyte,.which comprises con-. necting such structure at spaced joints with plural negative poles of a source of direct current alternately supplied in low"frequency. to said. poles,'and connecting a positive pole of said source through a resistance ,with such structure at still,

another point.

3. The method of protecting'a corrodible me tallic structure against deterioration in contact with an aqueous electrolyte, which comprises connecting'such structure at'spaced points ,with plural negative poles of a source of direct current alternately supplied in low frequency .to said poles,while maintaining a positive' pole of such source in electrical connection with such 'struc' ture through the medium of the liquid therein.

4. The method of protecting a corrodible me-- tallic structure against deteriorationjin contact with an aqueous electrolyte, which comprises connecting such structure at spaced points with plural negative poles of a 'sourceof direct current alternately supplied in low frequency to said poles, while maintaining a positive pole .of such source in electrical connection with such structure through the medium of a resistance ground cm L cuit.

5. The method of protecting a corrodible me-Q tallic structure against deterioration in contactf with anaqueous electrolyte, which comprises con-1,: necting such structure at spaced p ints witnpiu-v 1 ral negative poles of a source of direct current alternately supplied in low frequency to said poles, while maintaining a positive pole of such source in electrical connection with such structure through the medium of a ground circuit in-- cluding an adjustable resistance.

6. The method of protecting a corrodible metallic structure against deterioration in contact with an aqueous electrolyte, which comprises connecting such structure at two spaced points with the respective independent negative terminals of two half-wave rectifiers having independent negative terminals and a common positiveterminal and being supplied by alternating current, while maintaining the common positive terminal of such rectifiers in electrical connection with such structure.

7. The method of protecting a corrodible me tallic structure against deterioration in contact with an aqueous electrolyte, which comprises connecting such structure at two spaced points with the respective independent negative terminals of two half-wave rectifiers having a common positive terminal and independent negative terminals and being supplied by alternating current, while maintaining the common positive terminal of such rectifiers in electrical connection with such structure through the medium of the liquid therein.

8. The method of protecting a corrodible metallic structure against deterioration in contact with an aqueous electrolyte, which comprises connecting such structure at two spaced points with the respective independent negative terminals of two half-Wave rectifiers having a common positive terminal and independent negative terminals and being supplied by alternating current, while maintaining the common positive terminal of such rectifiers in electrical connection with such structure through the medium of a resistance ground circuit.

9. The method of protecting a corrodible metallic structure against deterioration in contact with an aqueous electrolyte, which comprises alternately impressing in low frequency atspaced apart points on such structure electric pulsations consisting of electro-negative potential pulsations, While including in circuit therewith liquid in contact with such metallic structure.

10. The combination with a corrodible metallic structure, of means for protecting the same against deterioration in contact with an aqueous electrolyte, comprising half-wave rectifiers supplied by alternating current and having their independent negative poles connected respectively to spaced points on said structure, and

their common positive pole also being in circuit with said structure.

11. The combination with a corrodible metallic structure, of means for protecting the same against deterioration in contact with an aqueous electrolyte, comprising a circuit of half-wave rectifiers supplied by alternating current and having a common positive terminal and independent negative terminals, concluotors connecting the respective negative terminals with spaced points on said structure, and the common positive terminal of said rectifiers having independent electrical connection with said structure.

12. The combination with a corrodible liquidcontaining metallic structure, of means for protecting the same against deterioration in contact with an aqueous electrolyte, comprising half-wave units supplied by alternating current and having a common negative positive terminal and independent negative terminals, conductors connecting the respective negative terminals with spaced points on said structure. and the common positive terminal of said rectifiers being electrically connected with said structure through the medium of the liquid therein.

13. The combination with a corrodible liquidcontaining metallic structure, of means for protecting the same against deterioration in contact with an aqueous electrolyte, comprising halfwave rectifiers supplied by alternating current and having a common positive terminal and independent negative terminals, conductors connecting the respective negative terminals with spaced points on said structure, and the common positive terminal of said rectifiers being electrically connected with said structure through the medium of a resistance ground circuit.

ARTHUR B. MACTAGGART. GEORGE J. THOMSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,053,214 Brown Sept. 1, 1936 2,176,514 Thomson Oct. 17, 1939 1,962,696 Rhodes June 12, 1934 1,437,507 Fink Dec. 5, 1922 1,436,686 Schnetzer Nov. 28, 1922 1,964,704 Erenyi June 26, 1934 2,219,738 Copson Oct. 29, 1940 1,877,389 Daum Sept. 13, 1932 FOREIGN PATENTS Number Country Date 716,453 France Oct. 6, 1931 645,856 France July 3, 1928 OTHER REFERENCE S McKinney, article in Transactions of The Electrochemical Society, vol. 75, pp. 34 and 35 (1938).

Publication, Status of Cathodic Protection Lines in 1941, by K. H. Logan, pp. 3 through 6.

Book, Electrochemistry, by Creighton (John Wiley 8: Sons, 1924), p. 239. 

